Organic electroluminescent materials and devices

ABSTRACT

A compound of the formula ML A L B  where ligand L A  is of Formula I, and ligand L B  is of Formula II below. 
     
       
         
         
             
             
         
       
         
         
           
             M is selected from Os(II) or Ru(II), and the compound ML A L B  has a formal neutral charge; and rings A, B, C, D, E, and F are independently a 5-membered or 6-membered aromatic ring, and R A , R B , R C , R D , R E , and R F  each independently represent mono to the maximum allowable substitution, or no substitution. 
             L 1 , L 2 , L 3 , and L 4  independently represent a single bond or an organic linking group; 
             W 1 , W 2 , W 3 , and W 4  are independently selected from carbon or nitrogen; 
             Y 1 , Y 2 , Y 3 , and Y 4  are independently selected from carbon or nitrogen; and 
             Z 1 , Z 2 , and Z 3  are independently selected from carbon or nitrogen, and at least one of Z 1 , Z 2 , and Z 3  is nitrogen. An organic electroluminescent device that includes an anode, a cathode, and an organic layer comprising a compound of the formula ML A L B  where ligand L A  is of Formula I, and ligand L B  is of Formula II above. A consumer product comprising an organic light-emitting device (OLED) above.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S.Provisional Application No. 62/598,571, filed Dec. 14, 2017, the entirecontents of which are incorporated herein by reference.

FIELD

The present invention relates to compounds for use as emitters, anddevices, such as organic light emitting diodes, including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting diodes/devices (OLEDs), organic phototransistors, organicphotovoltaic cells, and organic photodetectors. For OLEDs, the organicmaterials may have performance advantages over conventional materials.For example, the wavelength at which an organic emissive layer emitslight may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Alternatively the OLED can be designed to emit white light. Inconventional liquid crystal displays emission from a white backlight isfiltered using absorption filters to produce red, green and blueemission. The same technique can also be used with OLEDs. The white OLEDcan be either a single EML device or a stack structure. Color may bemeasured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processable” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY

A compound of the formula ML_(A)L_(B) where ligand L_(A) is of FormulaI, and ligand L_(B) is of Formula II below.

wherein

M is selected from Os(II) or Ru(II), and the compound ML_(A)L_(B) has aformal neutral charge;

rings A, B, C, D, E, and F are independently a 5-membered or 6-memberedaromatic ring, and R^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) eachindependently represent mono to the maximum allowable substitution, orno substitution;

L¹, L², L³, and L⁴ independently represent a single bond or an organiclinking group;

W¹, W², W³, and W⁴ are independently selected from carbon or nitrogen;

Y¹, Y², Y³, and Y⁴ are independently selected from carbon or nitrogen;

Z¹, Z², and Z³ are independently selected from carbon or nitrogen, andat least one of Z¹, Z², and Z³ is nitrogen;

wherein each R^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) areindependently hydrogen or a substituent selected from the groupconsisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl,heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylicacid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof, or optionally, any two adjacentsubstituents of R^(A), R^(B), R^(C), R^(D), R^(E), or R^(F), can join toform a ring.

An organic electroluminescent device that includes an anode, a cathode,and an organic layer comprising a compound of the formula ML_(A)L_(B)where ligand L_(A) is of Formula I, and ligand L_(B) is of Formula IIabove.

A consumer product comprising an organic light-emitting device (OLED),the OLED including an anode, a cathode, and an organic layer comprisinga compound of the formula ML_(A)L_(B) where ligand L_(A) is of FormulaI, and ligand L_(B) is of Formula II above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

DETAILED DESCRIPTION

Our prior work with bis-tridentate metal compounds and their applicationas phosphorescent emitters in OLEDs is described in WO 2009/046266,assigned to Universal Display Corporation, hereafter, the '266Publication. One interest at that time was to develop phosphorescentemitters that emit in the blue region of the visible spectrum. Thegeneral structure of the tridentate ligand is shown below where ring Arepresents an aromatic ring system with two to four fused rings, ring Brepresents a 5- or 6-membered aromatic ring or an aromatic ring systemas in ring A, and M is a second or third row transition metal.

Compounds of particular interest were neutral homoleptic compounds ofRu(II) or Os(II) with both ring A and ring B as cyclic N—N carbenesbridged by a central benzene ring. For example, some examples of ring Aand ring B cyclic carbenes, and a particular Os(II) compound are shownbelow. The calculated triplet T1 energy values for es-1 was 496 nm, andtherefore emit in a deep green region of the visible spectrum. Ourpresent interest is to a similar class of bis-tridentate Os(II) orRu(II) compounds, which emit in the yellow to orange to red and eveninto the infra-red region of the spectrum, e.g., from about 560 nm toabout 1200 nm, which is a very significant operation design range,particularly into the near-IR. To achieve this objective we investigateda class of heteroleptic bis-tridentate Os(II) and Ru(II) complexes, andto our surprise we observed not just a small shift, but rather asignificant red shift in the emission from the prior homoleptic Os(II)carbene compounds of the '266 Publication.

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), are incorporated byreference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and organic vaporjet printing (OVJP). Other methods may also be used. The materials to bedeposited may be modified to make them compatible with a particulardeposition method. For example, substituents such as alkyl and arylgroups, branched or unbranched, and preferably containing at least 3carbons, may be used in small molecules to enhance their ability toundergo solution processing. Substituents having 20 carbons or more maybe used, and 3-20 carbons is a preferred range. Materials withasymmetric structures may have better solution processability than thosehaving symmetric structures, because asymmetric materials may have alower tendency to recrystallize. Dendrimer substituents may be used toenhance the ability of small molecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention canbe incorporated into a wide variety of electronic component modules (orunits) that can be incorporated into a variety of electronic products orintermediate components. Examples of such electronic products orintermediate components include display screens, lighting devices suchas discrete light source devices or lighting panels, etc. that can beutilized by the end-user product manufacturers. Such electroniccomponent modules can optionally include the driving electronics and/orpower source(s). Devices fabricated in accordance with embodiments ofthe invention can be incorporated into a wide variety of consumerproducts that have one or more of the electronic component modules (orunits) incorporated therein. A consumer product comprising an OLED thatincludes the compound of the present disclosure in the organic layer inthe OLED is disclosed. Such consumer products would include any kind ofproducts that include one or more light source(s) and/or one or more ofsome type of visual displays. Some examples of such consumer productsinclude flat panel displays, curved displays, computer monitors, medicalmonitors, televisions, billboards, lights for interior or exteriorillumination and/or signaling, heads-up displays, fully or partiallytransparent displays, flexible displays, rollable displays, foldabledisplays, stretchable displays, laser printers, telephones, mobilephones, tablets, phablets, personal digital assistants (PDAs), wearabledevices, laptop computers, digital cameras, camcorders, viewfinders,micro-displays (displays that are less than 2 inches diagonal), 3-Ddisplays, virtual reality or augmented reality displays, vehicles, videowalls comprising multiple displays tiled together, theater or stadiumscreen, a light therapy device, and a sign. Various control mechanismsmay be used to control devices fabricated in accordance with the presentinvention, including passive matrix and active matrix. Many of thedevices are intended for use in a temperature range comfortable tohumans, such as 18 degrees C. to 30 degrees C., and more preferably atroom temperature (20-25 degrees C.), but could be used outside thistemperature range, for example, from −40 degree C. to +80 degree C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The terms “halo,” “halogen,” and “halide” are used interchangeably andrefer to fluorine, chlorine, bromine, and iodine.

The term “acyl” refers to a substituted carbonyl radical (C(O)—R_(s)).

The term “ester” refers to a substituted oxycarbonyl (—O—C(O)—R_(s) or—C(O)—O—R_(s)) radical.

The term “ether” refers to an —OR_(s) radical.

The terms “sulfanyl” or “thio-ether” are used interchangeably and referto a —SR_(s) radical.

The term “sulfinyl” refers to a —S(O)—R_(s) radical.

The term “sulfonyl” refers to a —SO₂—R_(s) radical.

The term “phosphino” refers to a —P(R_(s))₃ radical, wherein each R_(s)can be same or different.

The term “silyl” refers to a —Si(R_(s))₃ radical, wherein each R_(s) canbe same or different.

In each of the above, R_(s) can be hydrogen or a substituent selectedfrom the group consisting of deuterium, halogen, alkyl, cycloalkyl,heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, andcombination thereof. Preferred R_(s) is selected from the groupconsisting of alkyl, cycloalkyl, aryl, heteroaryl, and combinationthereof.

The term “alkyl” refers to and includes both straight and branched chainalkyl radicals. Preferred alkyl groups are those containing from one tofifteen carbon atoms and includes methyl, ethyl, propyl, 1-methylethyl,butyl, 1-methylpropyl, 2-methylpropyl, pentyl, 1-methylbutyl,2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl,2,2-dimethylpropyl, and the like. Additionally, the alkyl group isoptionally substituted.

The term “cycloalkyl” refers to and includes monocyclic, polycyclic, andspiro alkyl radicals. Preferred cycloalkyl groups are those containing 3to 12 ring carbon atoms and includes cyclopropyl, cyclopentyl,cyclohexyl, bicyclo[3.1.1]heptyl, spiro[4.5]decyl, spiro[5.5]undecyl,adamantyl, and the like. Additionally, the cycloalkyl group isoptionally substituted.

The terms “heteroalkyl” or “heterocycloalkyl” refer to an alkyl or acycloalkyl radical, respectively, having at least one carbon atomreplaced by a heteroatom. Optionally the at least one heteroatom isselected from O, S, N, P, B, Si and Se, preferably, O, S or N.Additionally, the heteroalkyl or heterocycloalkyl group is optionallysubstituted.

The term “alkenyl” refers to and includes both straight and branchedchain alkene radicals. Alkenyl groups are essentially alkyl groups thatinclude at least one carbon-carbon double bond in the alkyl chain.Cycloalkenyl groups are essentially cycloalkyl groups that include atleast one carbon-carbon double bond in the cycloalkyl ring. The term“heteroalkenyl” as used herein refers to an alkenyl radical having atleast one carbon atom replaced by a heteroatom. Optionally the at leastone heteroatom is selected from O, S, N, P, B, Si, and Se, preferably,O, S, or N. Preferred alkenyl, cycloalkenyl, or heteroalkenyl groups arethose containing two to fifteen carbon atoms. Additionally, the alkenyl,cycloalkenyl, or heteroalkenyl group is optionally substituted.

The term “alkynyl” refers to and includes both straight and branchedchain alkyne radicals. Preferred alkynyl groups are those containing twoto fifteen carbon atoms. Additionally, the alkynyl group is optionallysubstituted.

The terms “aralkyl” or “arylalkyl” are used interchangeably and refer toan alkyl group that is substituted with an aryl group. Additionally, thearalkyl group is optionally substituted.

The term “heterocyclic group” refers to and includes aromatic andnon-aromatic cyclic radicals containing at least one heteroatom.Optionally the at least one heteroatom is selected from O, S, N, P, B,Si, and Se, preferably, O, S, or N. Hetero-aromatic cyclic radicals maybe used interchangeably with heteroaryl. Preferred hetero-non-aromaticcyclic groups are those containing 3 to 7 ring atoms which includes atleast one hetero atom, and includes cyclic amines such as morpholino,piperidino, pyrrolidino, and the like, and cyclic ethers/thio-ethers,such as tetrahydrofuran, tetrahydropyran, tetrahydrothiophene, and thelike. Additionally, the heterocyclic group may be optionallysubstituted.

The term “aryl” refers to and includes both single-ring aromatichydrocarbyl groups and polycyclic aromatic ring systems. The polycyclicrings may have two or more rings in which two carbons are common to twoadjoining rings (the rings are “fused”) wherein at least one of therings is an aromatic hydrocarbyl group, e.g., the other rings can becycloalkyls, cycloalkenyls, aryl, heterocycles, and/or heteroaryls.Preferred aryl groups are those containing six to thirty carbon atoms,preferably six to twenty carbon atoms, more preferably six to twelvecarbon atoms. Especially preferred is an aryl group having six carbons,ten carbons or twelve carbons. Suitable aryl groups include phenyl,biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene,anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene,perylene, and azulene, preferably phenyl, biphenyl, triphenyl,triphenylene, fluorene, and naphthalene. Additionally, the aryl group isoptionally substituted.

The term “heteroaryl” refers to and includes both single-ring aromaticgroups and polycyclic aromatic ring systems that include at least oneheteroatom. The heteroatoms include, but are not limited to O, S, N, P,B, Si, and Se. In many instances, O, S, or N are the preferredheteroatoms. Hetero-single ring aromatic systems are preferably singlerings with 5 or 6 ring atoms, and the ring can have from one to sixheteroatoms. The hetero-polycyclic ring systems can have two or morerings in which two atoms are common to two adjoining rings (the ringsare “fused”) wherein at least one of the rings is a heteroaryl, e.g.,the other rings can be cycloalkyls, cycloalkenyls, aryl, heterocycles,and/or heteroaryls. The hetero-polycyclic aromatic ring systems can havefrom one to six heteroatoms per ring of the polycyclic aromatic ringsystem. Preferred heteroaryl groups are those containing three to thirtycarbon atoms, preferably three to twenty carbon atoms, more preferablythree to twelve carbon atoms. Suitable heteroaryl groups includedibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene,benzofuran, benzothiophene, benzoselenophene, carbazole,indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole,triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole,thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine,oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole,indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline,isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine,phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine,phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine,preferably dibenzothiophene, dibenzofuran, dibenzoselenophene,carbazole, indolocarbazole, imidazole, pyridine, triazine,benzimidazole, 1,2-azaborine, 1,3-azaborine, 1,4-azaborine, borazine,and aza-analogs thereof. Additionally, the heteroaryl group isoptionally substituted.

Of the aryl and heteroaryl groups listed above, the groups oftriphenylene, naphthalene, anthracene, dibenzothiophene, dibenzofuran,dibenzoselenophene, carbazole, indolocarbazole, imidazole, pyridine,pyrazine, pyrimidine, triazine, and benzimidazole, and the respectiveaza-analogs of each thereof are of particular interest.

The terms alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aralkyl, heterocyclic group, aryl,and heteroaryl, as used herein, are independently unsubstituted, orindependently substituted, with one or more general substituents.

In many instances, the general substituents are selected from the groupconsisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl,heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylicacid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof.

In some instances, the preferred general substituents are selected fromthe group consisting of deuterium, fluorine, alkyl, cycloalkyl,heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, andcombinations thereof.

In some instances, the preferred general substituents are selected fromthe group consisting of deuterium, fluorine, alkyl, cycloalkyl, alkoxy,aryloxy, amino, silyl, aryl, heteroaryl, sulfanyl, and combinationsthereof.

In yet other instances, the more preferred general substituents areselected from the group consisting of deuterium, fluorine, alkyl,cycloalkyl, aryl, heteroaryl, and combinations thereof.

The terms “substituted” and “substitution” refer to a substituent otherthan H that is bonded to the relevant position, e.g., a carbon ornitrogen. For example, when R¹ represents mono-substitution, then one R¹must be other than H (i.e., a substitution). Similarly, when R¹represents di-substitution, then two of R¹ must be other than H.Similarly, when R¹ represents no substitution, R¹, for example, can be ahydrogen for available valencies of ring atoms, as in carbon atoms forbenzene and the nitrogen atom in pyrrole, or simply represents nothingfor ring atoms with fully filled valencies, e.g., the nitrogen atom inpyridine. The maximum number of substitutions possible in a ringstructure will depend on the total number of available valencies in thering atoms.

As used herein, “combinations thereof” indicates that one or moremembers of the applicable list are combined to form a known orchemically stable arrangement that one of ordinary skill in the art canenvision from the applicable list. For example, an alkyl and deuteriumcan be combined to form a partial or fully deuterated alkyl group; ahalogen and alkyl can be combined to form a halogenated alkylsubstituent; and a halogen, alkyl, and aryl can be combined to form ahalogenated arylalkyl. In one instance, the term substitution includes acombination of two to four of the listed groups. In another instance,the term substitution includes a combination of two to three groups. Inyet another instance, the term substitution includes a combination oftwo groups. Preferred combinations of substituent groups are those thatcontain up to fifty atoms that are not hydrogen or deuterium, or thosewhich include up to forty atoms that are not hydrogen or deuterium, orthose that include up to thirty atoms that are not hydrogen ordeuterium. In many instances, a preferred combination of substituentgroups will include up to twenty atoms that are not hydrogen ordeuterium.

The “aza” designation in the fragments described herein, i.e.aza-dibenzofuran, aza-dibenzothiophene, etc. means that one or more ofthe C—H groups in the respective fragment can be replaced by a nitrogenatom, for example, and without any limitation, azatriphenyleneencompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. Oneof ordinary skill in the art can readily envision other nitrogen analogsof the aza-derivatives described above, and all such analogs areintended to be encompassed by the terms as set forth herein.

As used herein, “deuterium” refers to an isotope of hydrogen. Deuteratedcompounds can be readily prepared using methods known in the art. Forexample, U.S. Pat. No. 8,557,400, Patent Pub. No. WO 2006/095951, andU.S. Pat. Application Pub. No. US 2011/0037057, which are herebyincorporated by reference in their entireties, describe the making ofdeuterium-substituted organometallic complexes. Further reference ismade to Ming Yan, et al., Tetrahedron 2015, 71, 1425-30 and Atzrodt etal., Angew. Chem. Int. Ed. (Reviews) 2007, 46, 7744-65, which areincorporated by reference in their entireties, describe the deuterationof the methylene hydrogens in benzyl amines and efficient pathways toreplace aromatic ring hydrogens with deuterium, respectively.

It is to be understood that when a molecular fragment is described asbeing a substituent or otherwise attached to another moiety, its namemay be written as if it were a fragment (e.g. phenyl, phenylene,naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g.benzene, naphthalene, dibenzofuran). As used herein, these differentways of designating a substituent or attached fragment are considered tobe equivalent.

The invention is directed to a compound of the formula ML_(A)L_(B) whereligand L_(A) is of Formula I and ligand L_(B) is of Formula II below.

wherein

M is selected from Os(II) or Ru(II), and the compound ML_(A)L_(B) has aformal neutral charge;

rings A, B, C, D, E, and F are independently a 5-membered or 6-memberedaromatic ring, and R^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) eachindependently represent mono to the maximum allowable substitution, orno substitution;

L¹, L², L³, and L⁴ independently represent a single bond or an organiclinking group;

W¹, W², W³, and W⁴ are independently selected from carbon or nitrogen;

Y¹, Y², Y³, and Y⁴ are independently selected from carbon or nitrogen;

Z¹, Z², and Z³ are independently selected from carbon or nitrogen, andat least one of Z¹, Z², and Z³ is nitrogen;

wherein each R^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) areindependently hydrogen or a substituent selected from the groupconsisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl,heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylicacid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof, or optionally, any two adjacentsubstituents of R^(A), R^(B), R^(C), R^(D), R^(E), or R^(F), can join toform a ring.

In one embodiment, R^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) areselected from hydrogen or a substituent selected from the groupconsisting of deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinationsthereof.

In one embodiment of the compounds ML_(A)L_(B), ligand L_(B) is furtherdefined by one of Z¹, Z², or Z³ as being nitrogen. In many instances,the one Z¹, Z², or Z³ nitrogen will form dative coordinate bonds withOs(II) or Ru(II), and the third of Z¹, Z², or Z³ will be a carbon. Forexample, ring E can be an optionally substituted benzene, naphthyl, oran aza-analog of each thereof, with Z² as carbon, and rings D and F arepyridyl or imidazole (Z¹ and Z³ are nitrogen). In another instance, oneof Z¹ or Z³ is nitrogen, and the other is a carbene carbon.

In one embodiment of the compounds ML_(A)L_(B), ligand L_(B) is furtherdefined by two of Z¹, Z², or Z³ as being nitrogen. In many instances,the two Z¹, Z², or Z³ nitrogen will form dative coordinate bonds withOs(II) or Ru(II), and the third of Z¹, Z², or Z³ will be a carbon. Forexample, ring E can be an optionally substituted benzene, naphthyl, oran aza-analog of each thereof, with Z² as carbon, and rings D and F arepyridyl or imidazole (Z¹ and Z³ are nitrogen). In another instance, oneof Z¹ or Z³ is nitrogen, and the other is a carbene carbon.

In one embodiment of the compounds ML_(A)L_(B), ligand L_(B) is furtherdefined by Z¹ as carbon, and ring D selected from an optionallysubstituted benzene, naphthyl, or an aza-analog of each thereof.Moreover, Z² and Z³ are nitrogen, or in another instance, one of Z² orZ³ is nitrogen, and the other is a carbene carbon.

In one embodiment of the compounds ML_(A)L_(B), ligand L_(B) is furtherdefined by Z³ as carbon, and ring F selected from an optionallysubstituted benzene, naphthyl, or an aza-analog of each thereof.Moreover, Z¹ and Z² are nitrogen, or in another instance, one of Z¹ orZ² is nitrogen, and the other is a carbene carbon.

In one embodiment of the compounds ML_(A)L_(B), and optionally, incombination with the ligand L_(B) embodiments above, ligand L_(A) willhave two of rings A, B, or C being an N-heterocyclic carbene ring, eachof which with a carbene carbon coordinated to Os(II) or Ru(II).

In another embodiment of the compounds ML_(A)L_(B), and optionally, incombination with the ligand L_(B) embodiments above, ring A and ring Care both N-heterocyclic carbene rings, each of which with a carbenecarbon coordinated to Os(II) or Ru(II). Also, ring B can be selectedfrom optionally substituted benzene, naphthyl, or an aza-analog of eachthereof.

In another embodiment of the compounds ML_(A)L_(B), or in any onepreferred embodiment of ligand L_(A) or ligand L_(B) above, L¹, L², L³,and L⁴ are each a direct bond.

In one embodiment of the compounds ML_(A)L_(B), or in any one preferredembodiment of ligand L_(A) or ligand L_(B) above, or where L¹, L², L³,and L⁴ are each a direct bond, each of W¹, W², W³, and W⁴ are carbon,and ring B is an optionally substituted benzene. In another embodiment,one or two of W¹, W², W³, or W⁴ are nitrogen, preferably, W¹ and/or W²are nitrogen, particularly if rings A and/or C are N-heterocycliccarbene ligand groups.

Of particular interest, are compounds ML_(A)L_(B), ligand L_(A) isselected from the group consisting of

wherein

X¹, X², X³, X⁴, and X⁵ are independently selected from C or N;

R, R′, R¹, R², and R³ are independently hydrogen or a substituentselected from the group consisting of deuterium, halogen, alkyl,cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carboxylic acid, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof; or optionally,any two adjacent substituents of R¹, R², and R³ can join to form a ringwith ring.

In another embodiment, the above compounds of particular interest willhave R^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) as being selected fromhydrogen or a substituent selected from the group consisting ofdeuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl,nitrile, isonitrile, sulfanyl, and combinations thereof.

In another embodiment, the above compounds of particular interest willhave each of X¹, X², and X³ is C, and form a benzene ring, which isoptionally substituted with R².

In another embodiment, the above compounds of particular interest willhave two of R¹, two of R², and/or two of R³ join to form a fused benzenering or an aza-analog thereof. Again, each fused ring is optionallysubstituted. One reason for fusing an aromatic ring, preferably, a6-membered aromatic ring to one or more of rings A, B, or C of ligandL_(A) is to provide additional red shift in the emission spectrum of thecompounds ML_(A)L_(B), infra.

Select compounds of ML_(A)L_(B) will have a ligand L_(A) of Formula Iselected from the group consisting of

Select compounds of ML_(A)L_(B) will have a ligand L_(B) of Formula IIselected from the group consisting of

wherein

X⁶, X⁷, X⁸, X⁹, X¹⁰, X¹¹, X¹², X¹³, and X¹⁴ are each independentlyselected from C or N, and each 6-membered aromatic ring has no more thanthree N;

R″, R⁴, R⁵, and R⁶ are independently hydrogen or a substituent selectedfrom the group consisting of deuterium, halogen, alkyl, cycloalkyl,heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; or optionally, any twoadjacent substituents of R⁴, R⁵, and R⁶ can join to form a ring withring.

Select embodiments of ligand L_(B) will have R⁴, R⁵, and R⁶ selectedfrom hydrogen or a substituent selected from the group consisting ofdeuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl,nitrile, isonitrile, sulfanyl, and combinations thereof.

In another embodiment, the compounds with the select embodiments ofL_(B) will have each of X⁶, X⁷, and X⁸ as carbon, and form a benzene orpyridine ring, which is optionally substituted with R⁴. In anotherembodiment, the compounds with the select embodiments of L_(B) will haveeach of X⁹, X¹⁰, and X¹¹ as carbon, and form a benzene or pyridine ring,which is optionally substituted with R⁵. In another embodiment, thecompounds with the select embodiments of L_(B) will have each of X¹²,X¹³, and X¹⁴ as carbon, and form a benzene or pyridine ring, which isoptionally substituted with R⁶.

In another embodiment, the above compounds with the select embodimentsof L_(B) will have two of R⁴, two of R⁵, and/or two of R⁶ join to form afused benzene ring or an aza-analog thereof. Again, each fused ring isoptionally substituted. One reason for fusing an aromatic ring,preferably, a 6-membered aromatic ring to one or more of rings D, E, orF of ligand L_(B) is to provide additional red shift in the emissionspectrum of the compounds ML_(A)L_(B), infra.

Compounds of particular interest will include any one of the selectligands LB above in combination with any one ligand LA selected from thegroup consisting of L_(A1) to L_(A68) identified above.

Select compounds of ML_(A)L_(B) will have a ligand L_(B) of Formula IIselected from the group consisting of

We also describe a very select structural list of the compoundsML_(A)L_(B). These compounds can be assigned or identified as a Compoundx having the formula M(L_(Ai))(L_(Bj)); wherein x=151i+j−151; a is aninteger from 1 to 68; and j is an integer from 1 to 151. Ligand L_(Ai)will have a structure selected from ligand L_(A1) to LA₆₈, and LigandL_(Bj) will have a structure selected from ligand L_(B1) to LA_(B151).

We also describe an organic light emitting device (OLED) comprising ananode, a cathode, and an organic layer disposed between the anode andthe cathode, the organic layer comprising a compound of the formulaML_(A)L_(B); wherein ligand L_(A) is of Formula I, and ligand L_(B) isof Formula II

wherein

M is selected from Os(II) or Ru(II), and the compound ML_(A)L_(B) has aformal neutral charge;

rings A, B, C, D, E, and F are independently a 5-membered or 6-memberedaromatic ring, and R^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) eachindependently represent mono to the maximum allowable substitution, orno substitution;

L¹, L², L³, and L⁴ independently represent a single bond or an organiclinking group;

W¹, W², W³, and W⁴ are independently selected from carbon or nitrogen;

Y¹, Y², Y³, and Y⁴ are independently selected from carbon or nitrogen;

Z¹, Z², and Z³ are independently selected from carbon or nitrogen, andat least one of Z¹, Z², and Z³ is nitrogen;

wherein each R^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) areindependently hydrogen or a substituent selected from the groupconsisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl,heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylicacid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof, or optionally, any two adjacentsubstituents of R^(A), R^(B), R^(C), R^(D), R^(E), or R^(F), can join toform a ring.

The compounds of ML_(A)L_(B) where ligand L_(A) is of Formula I andligand L_(B) is of Formula II provides an extraordinary opportunity tocolor tune the emission of an OLED from green (compound 5 and 6), yellow(compound 3 and 4), red (compound 2) and even into the near-IR range(compound 7, 8 and 9). As indicated by the DFT data of Table 1 (see,experimental) the heteroleptic, bis tridenate Os(II)-carbene compounds,e.g. compounds 2-9, provide an operating design range to extend thelight emission of a phosphorescent OLED from about 550 nm to about 1200nm by simply changing out the bis-carbene ligand of Comparative Example1 (CE1) for a tridentate L_(B) ligand with a coordinating quinazoline(Compound 2) at one of the six octahedral sites—there is no other changein the octahedral environment about the Os(II). The red shift in thisinstance is a huge red-shift of about 275 nm from CE1 to Compound 2.Similar comparisons can be made between CE1 and any one of Compounds 3to 9. For example, the switching out of another octahedral site withanother quinazoline as in Compound 9 provides a red shift of about 677nm.

Of particular interest are compounds ML_(A)L_(B) where ligand L_(A) isof Formula I and ligand L_(B) is of Formula II that emit in the near-IRregion of the spectrum, i.e., from 700 nm to 1200 nm, from 800 nm to1200 nm, from 900 nm to 1200 nm, and from 1000 nm to 1200 nm.

In some embodiments, the OLED has one or more characteristics selectedfrom the group consisting of being flexible, being rollable, beingfoldable, being stretchable, and being curved. In some embodiments, theOLED is transparent or semi-transparent. In some embodiments, the OLEDfurther comprises a layer comprising carbon nanotubes.

In some embodiments, the OLED further comprises a layer comprising adelayed fluorescent emitter. In some embodiments, the OLED comprises aRGB pixel arrangement or white plus color filter pixel arrangement. Insome embodiments, the OLED is a mobile device, a hand held device, or awearable device. In some embodiments, the OLED is a display panel havingless than 10 inch diagonal or 50 square inch area. In some embodiments,the OLED is a display panel having at least 10 inch diagonal or 50square inch area. In some embodiments, the OLED is a lighting panel.

According to another aspect, an emissive region in an OLED (e.g., theorganic layer described herein) is disclosed. The emissive regioncomprises a first compound as described herein. In some embodiments, thefirst compound in the emissive region is an emissive dopant or anon-emissive dopant. In some embodiments, the emissive dopant furthercomprises a host, wherein the host comprises at least one selected fromthe group consisting of metal complex, triphenylene, carbazole,dibenzothiophene, dibenzofuran, dibenzoselenophene, aza-triphenylene,aza-carbazole, aza-dibenzothiophene, aza-dibenzofuran, andaza-dibenzoselenophene. In some embodiments, the emissive region furthercomprises a host, wherein the host is selected from the group consistingof:

and combinations thereof.

The organic layer can also include a host. In some embodiments, two ormore hosts are preferred. In some embodiments, the hosts used may be a)bipolar, b) electron transporting, c) hole transporting or d) wide bandgap materials that play little role in charge transport. In someembodiments, the host can include a metal complex. The host can be atriphenylene containing benzo-fused thiophene or benzo-fused furan. Anysubstituent in the host can be an unfused substituent independentlyselected from the group consisting of C_(n)H_(2n+1), OC_(n)H_(2n+1),OAr₁, N(C_(n)H_(2n+1))₂, N(Ar₁)(Ar₂), CH═CH—C_(n)H_(2n+1),C≡C—C_(n)H_(2n+1), Ar₁, Ar₁—Ar₂, and C_(n)H_(2n)—Ar₁, or the host has nosubstitutions. In the preceding substituents n can range from 1 to 10;and Ar₁ and Ar₂ can be independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof. The host can be an inorganic compound.For example a Zn containing inorganic material e.g. ZnS.

In some embodiments, the compound can be an emissive dopant. In someembodiments, the compound can produce emissions via phosphorescence,fluorescence, thermally activated delayed fluorescence, i.e., TADF (alsoreferred to as E-type delayed fluorescence; see, e.g., U.S. applicationSer. No. 15/700,352, which is hereby incorporated by reference in itsentirety), triplet-triplet annihilation, or combinations of theseprocesses. In some embodiments, the emissive dopant can be a racemicmixture, or can be enriched in one enantiomer.

According to another aspect, a formulation comprising the compounddescribed herein is also disclosed.

The OLED disclosed herein can be incorporated into one or more of aconsumer product, an electronic component module, and a lighting panel.The organic layer can be an emissive layer and the compound can be anemissive dopant in some embodiments, while the compound can be anon-emissive dopant in other embodiments.

In yet another aspect of the present disclosure, a formulation thatcomprises the novel compound disclosed herein is described. Theformulation can include one or more components selected from the groupconsisting of a solvent, a host, a hole injection material, holetransport material, electron blocking material, hole blocking material,and an electron transport material, disclosed herein.

Combination with Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

Conductivity Dopants:

A charge transport layer can be doped with conductivity dopants tosubstantially alter its density of charge carriers, which will in turnalter its conductivity. The conductivity is increased by generatingcharge carriers in the matrix material, and depending on the type ofdopant, a change in the Fermi level of the semiconductor may also beachieved. Hole-transporting layer can be doped by p-type conductivitydopants and n-type conductivity dopants are used in theelectron-transporting layer.

Non-limiting examples of the conductivity dopants that may be used in anOLED in combination with materials disclosed herein are exemplifiedbelow together with references that disclose those materials:EP01617493, EP01968131, EP2020694, EP2684932, US20050139810,US20070160905, US20090167167, US2010288362, WO06081780, WO2009003455,WO2009008277, WO2009011327, WO2014009310, US2007252140, US2015060804,US20150123047, and US2012146012.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but are not limited to: aphthalocyanine or porphyrin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and across-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, butnot limit to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting of aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, and azulene; the group consistingof aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran,benzothiophene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and the group consisting of 2 to 10 cyclic structural units which aregroups of the same type or different types selected from the aromatichydrocarbon cyclic group and the aromatic heterocyclic group and arebonded to each other directly or via at least one of oxygen atom,nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom,chain structural unit and the aliphatic cyclic group. Each Ar may beunsubstituted or may be substituted by a substituent selected from thegroup consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl,heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylicacids, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH)or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but are notlimited to the following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40;(Y¹⁰¹-Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independentlyselected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and k′+k″ is the maximum number of ligands thatmay be attached to the metal.

In one aspect, (Y¹⁰¹-Y¹⁰²) is a 2-phenylpyridine derivative. In anotheraspect, (Y¹⁰¹-Y¹⁰²) is a carbene ligand. In another aspect, Met isselected from Ir, Pt, Os, and Zn. In a further aspect, the metal complexhas a smallest oxidation potential in solution vs. Fc⁺/Fc couple lessthan about 0.6 V.

Non-limiting examples of the HIL and HTL materials that may be used inan OLED in combination with materials disclosed herein are exemplifiedbelow together with references that disclose those materials:CN102702075, DE102012005215, EP01624500, EP01698613, EP01806334,EP01930964, EP01972613, EP01997799, EP02011790, EP02055700, EP02055701,EP1725079, EP2085382, EP2660300, EP650955, JP07-073529, JP2005112765,JP2007091719, JP2008021687, JP2014-009196, KR20110088898, KR20130077473,TW201139402, U.S. Ser. No. 06/517,957, US20020158242, US20030162053,US20050123751, US20060182993, US20060240279, US20070145888,US20070181874, US20070278938, US20080014464, US20080091025,US20080106190, US20080124572, US20080145707, US20080220265,US20080233434, US20080303417, US2008107919, US20090115320,US20090167161, US2009066235, US2011007385, US20110163302, US2011240968,US2011278551, US2012205642, US2013241401, US20140117329, US2014183517,U.S. Pat. Nos. 5,061,569, 5,639,914, WO05075451, WO07125714, WO08023550,WO08023759, WO2009145016, WO2010061824, WO2011075644, WO2012177006,WO2013018530, WO2013039073, WO2013087142, WO2013118812, WO2013120577,WO2013157367, WO2013175747, WO2014002873, WO2014015935, WO2014015937,WO2014030872, WO2014030921, WO2014034791, WO2014104514, WO2014157018.

EBL:

An electron blocking layer (EBL) may be used to reduce the number ofelectrons and/or excitons that leave the emissive layer. The presence ofsuch a blocking layer in a device may result in substantially higherefficiencies, and/or longer lifetime, as compared to a similar devicelacking a blocking layer. Also, a blocking layer may be used to confineemission to a desired region of an OLED. In some embodiments, the EBLmaterial has a higher LUMO (closer to the vacuum level) and/or highertriplet energy than the emitter closest to the EBL interface. In someembodiments, the EBL material has a higher LUMO (closer to the vacuumlevel) and/or higher triplet energy than one or more of the hostsclosest to the EBL interface. In one aspect, the compound used in EBLcontains the same molecule or the same functional groups used as one ofthe hosts described below.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant. Any host material may be used with any dopant so long as thetriplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

wherein Met is a metal; (Y¹⁰³-Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴are independently selected from C, N, O, P, and S; L¹⁰¹ is an anotherligand; k′ is an integer value from 1 to the maximum number of ligandsthat may be attached to the metal; and k′+k″ is the maximum number ofligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O—N) is a bidentate ligand, having metal coordinated to atoms Oand N.

In another aspect, Met is selected from Ir and Pt. In a further aspect,(Y¹⁰³-Y¹⁰⁴) is a carbene ligand.

Examples of other organic compounds used as host are selected from thegroup consisting of aromatic hydrocarbon cyclic compounds such asbenzene, biphenyl, triphenyl, triphenylene, tetraphenylene, naphthalene,anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene,perylene, and azulene; the group consisting of aromatic heterocycliccompounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene,furan, thiophene, benzofuran, benzothiophene, benzoselenophene,carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole,imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole,dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine,triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole,indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole,quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline,naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine,phenothiazine, phenoxazine, benzofuropyridine, furodipyridine,benzothienopyridine, thienodipyridine, benzoselenophenopyridine, andselenophenodipyridine; and the group consisting of 2 to 10 cyclicstructural units which are groups of the same type or different typesselected from the aromatic hydrocarbon cyclic group and the aromaticheterocyclic group and are bonded to each other directly or via at leastone of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorusatom, boron atom, chain structural unit and the aliphatic cyclic group.Each option within each group may be unsubstituted or may be substitutedby a substituent selected from the group consisting of deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carboxylic acids, ether, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

In one aspect, the host compound contains at least one of the followinggroups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen,deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acids, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof, and when it is aryl or heteroaryl, it has thesimilar definition as Ar's mentioned above. k is an integer from 0 to 20or 1 to 20. X¹⁰¹ to X¹⁰⁸ are independently selected from C (includingCH) or N. Z¹⁰¹ and Z¹⁰² are independently selected from NR¹⁰¹, O, or S.

Non-limiting examples of the host materials that may be used in an OLEDin combination with materials disclosed herein are exemplified belowtogether with references that disclose those materials: EP2034538,EP2034538A, EP2757608, JP2007254297, KR20100079458, KR20120088644,KR20120129733, KR20130115564, TW201329200, US20030175553, US20050238919,US20060280965, US20090017330, US20090030202, US20090167162,US20090302743, US20090309488, US20100012931, US20100084966,US20100187984, US2010187984, US2012075273, US2012126221, US2013009543,US2013105787, US2013175519, US2014001446, US20140183503, US20140225088,US2014034914, U.S. Pat. No. 7,154,114, WO2001039234, WO2004093207,WO2005014551, WO2005089025, WO2006072002, WO2006114966, WO2007063754,WO2008056746, WO2009003898, WO2009021126, WO2009063833, WO2009066778,WO2009066779, WO2009086028, WO2010056066, WO2010107244, WO2011081423,WO2011081431, WO2011086863, WO2012128298, WO2012133644, WO2012133649,WO2013024872, WO2013035275, WO2013081315, WO2013191404, WO2014142472,US20170263869, US20160163995, U.S. Pat. No. 9,466,803,

Additional Emitters:

One or more additional emitter dopants may be used in conjunction withthe compound of the present disclosure. Examples of the additionalemitter dopants are not particularly limited, and any compounds may beused as long as the compounds are typically used as emitter materials.Examples of suitable emitter materials include, but are not limited to,compounds which can produce emissions via phosphorescence, fluorescence,thermally activated delayed fluorescence, i.e., TADF (also referred toas E-type delayed fluorescence), triplet-triplet annihilation, orcombinations of these processes.

Non-limiting examples of the emitter materials that may be used in anOLED in combination with materials disclosed herein are exemplifiedbelow together with references that disclose those materials:CN103694277, CN1696137, EB01238981, EP01239526, EP01961743, EP1239526,EP1244155, EP1642951, EP1647554, EP1841834, EP1841834B, EP2062907,EP2730583, JP2012074444, JP2013110263, JP4478555, KR1020090133652,KR20120032054, KR20130043460, TW201332980, U.S. Ser. Nos. 06/699,599,06/916,554, US20010019782, US20020034656, US20030068526, US20030072964,US20030138657, US20050123788, US20050244673, US2005123791, US2005260449,US20060008670, US20060065890, US20060127696, US20060134459,US20060134462, US20060202194, US20060251923, US20070034863,US20070087321, US20070103060, US20070111026, US20070190359,US20070231600, US2007034863, US2007104979, US2007104980, US2007138437,US2007224450, US2007278936, US20080020237, US20080233410, US20080261076,US20080297033, US200805851, US2008161567, US2008210930, US20090039776,US20090108737, US20090115322, US20090179555, US2009085476, US2009104472,US20100090591, US20100148663, US20100244004, US20100295032,US2010102716, US2010105902, US2010244004, US2010270916, US20110057559,US20110108822, US20110204333, US2011215710, US2011227049, US2011285275,US2012292601, US20130146848, US2013033172, US2013165653, US2013181190,US2013334521, US20140246656, US2014103305, U.S. Pat. Nos. 6,303,238,6,413,656, 6,653,654, 6,670,645, 6,687,266, 6,835,469, 6,921,915,7,279,704, 7,332,232, 7,378,162, 7,534,505, 7,675,228, 7,728,137,7,740,957, 7,759,489, 7,951,947, 8,067,099, 8,592,586, 8,871,361,WO06081973, WO06121811, WO07018067, WO07108362, WO07115970, WO07115981,WO08035571, WO2002015645, WO2003040257, WO2005019373, WO2006056418,WO2008054584, WO2008078800, WO2008096609, WO2008101842, WO2009000673,WO2009050281, WO2009100991, WO2010028151, WO2010054731, WO2010086089,WO2010118029, WO2011044988, WO2011051404, WO2011107491, WO2012020327,WO2012163471, WO2013094620, WO2013107487, WO2013174471, WO2014007565,WO2014008982, WO2014023377, WO2014024131, WO2014031977, WO2014038456,WO2014112450.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies and/or longer lifetime as compared to a similar devicelacking a blocking layer. Also, a blocking layer may be used to confineemission to a desired region of an OLED. In some embodiments, the HBLmaterial has a lower HOMO (further from the vacuum level) and/or highertriplet energy than the emitter closest to the HBL interface. In someembodiments, the HBL material has a lower HOMO (further from the vacuumlevel) and/or higher triplet energy than one or more of the hostsclosest to the HBL interface.

In one aspect, compound used in HBL contains the same molecule or thesame functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of thefollowing groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ isan integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, compound used in ETL contains at least one of thefollowing groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen,deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acids, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof, when it is aryl or heteroaryl, it has the similardefinition as Ar's mentioned above. Ar¹ to Ar³ has the similardefinition as Ar's mentioned above. k is an integer from 1 to 20. X¹⁰¹to X¹⁰⁸ is selected from C (including CH) or N.

In another aspect, the metal complexes used in ETL contains, but notlimit to the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinatedto atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer valuefrom 1 to the maximum number of ligands that may be attached to themetal.

Non-limiting examples of the ETL materials that may be used in an OLEDin combination with materials disclosed herein are exemplified belowtogether with references that disclose those materials: CN103508940,EP01602648, EP01734038, EP01956007, JP2004-022334, JP2005149918,JP2005-268199, KR0117693, KR20130108183, US20040036077, US20070104977,US2007018155, US20090101870, US20090115316, US20090140637,US20090179554, US2009218940, US2010108990, US2011156017, US2011210320,US2012193612, US2012214993, US2014014925, US2014014927, US20140284580,U.S. Pat. Nos. 6,656,612, 8,415,031, WO2003060956, WO2007111263,WO2009148269, WO2010067894, WO2010072300, WO2011074770, WO2011105373,WO2013079217, WO2013145667, WO2013180376, WO2014104499, WO2014104535,

Charge Generation Layer (CGL)

In tandem or stacked OLEDs, the CGL plays an essential role in theperformance, which is composed of an n-doped layer and a p-doped layerfor injection of electrons and holes, respectively. Electrons and holesare supplied from the CGL and electrodes. The consumed electrons andholes in the CGL are refilled by the electrons and holes injected fromthe cathode and anode, respectively; then, the bipolar currents reach asteady state gradually. Typical CGL materials include n and pconductivity dopants used in the transport layers.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. may be undeuterated, partially deuterated, andfully deuterated versions thereof. Similarly, classes of substituentssuch as, without limitation, alkyl, aryl, cycloalkyl, heteroaryl, etc.also may be undeuterated, partially deuterated, and fully deuteratedversions thereof.

EXPERIMENTAL Synthesis of 1,3-bis(1H-benzo[d]imidazol-1-yl)benzene,Ligand L_(A36)

In a 1 L round-bottomed flask 1,3-diiodobenzene (26.43 g, 80 mmol),1H-benzo[d]imidazole (20.82 g, 176 mmol), and 1,10-phenanthroline (5.77g, 32.0 mmol), CuI (3.05 g, 16 mmol), and cesium carbonate (120 g, 369mmol) is combined in anhydrous DMF (350 mL) to give a brown suspension.The reaction is purged with N₂ for 20 minutes and then heated to refluxfor 24 hrs. The reaction mixture is passed thought a plug of silica gel(5% MeOH in DCM) to obtain the crude product. The crude product issubjected to silica gel chromatography (400 g, 2% MeOH to 5% MeOH inDCM) to ultimately obtain the final product (12.66 g, 51%).

In a 1 L round bottom flask, compound A (12.66 g, 40.8 mmol),iodomethane (25.5 mL, 408 mmol) were combined in DMF (500 mL) to give ayellow solution. The reaction mixture was heated to 42° C. for 24 hrsand filtered to get the product, ligand L_(A36) (21.69 g, 89%).

Synthesis of 1,3-bis(3H-imidazo[4,5-b]pyridin-3-yl)benzene

A 500 mL round-bottomed flask is charged with 1H-imidazo[4,5-b]pyridine(12.7 g, 107 mmol), 1,3-diiodobenzene (17.65 g, 53.5 mmol), copper (I)oxide (0.176 g, 1.231 mmol), 4,7-dimethoxy-1,10-phenanthroline (0.591 g,2.46 mmol), cesium carbonate (48.8 g, 150 mmol), polyethylene glycol(9.79 g, D=1.088, 9 mL) and DMSO (125 mL) The reaction mixture is vacuumevacuated and back filled with N₂ three times. The reaction mixture isheated to 110° C. for 24 hours. The reaction mixture was decanted intowater (500 mL) and filtered. The precipitate is collected subjected tocolumn chromatography (5% MeOH in DCM) to yield the desired product (6g, 36%). The reaction with iodomethane as described above provides thecorresponding bis(Me-imidazole analog.

The synthesis of the tridentate ligands L_(B) are prepared in a mannersimilar to the tridentate ligand L_(A) above, and in accordance with thesynthetic chemistry described in U.S. Pat. No. 8,754,232, which isassigned to Universal Display Corporation. The corresponding Os(II) andRu(II) compounds ML_(A)L_(B) are made in accordance with the syntheticprocesses described in U.S. Pat. No. 7,754,232, assigned to UniversalDisplay Corporation, along with methods known to those of ordinary skillin the art.

TABLE 1 DFT Data of Select Compounds and Comparative Example 1 (CE 1)HOMO LUMO S1 T1 Ex. No. Compound (eV) (eV) (nm) (nm) CE 1

−4.54 −0.85 431 463 2

−4.558 −1.816 601 737 3

−4.472 −1.604 575 664 4

−4.422 −1.479 548 632 5

−4.423 −1.283 520 588 6

−4.463 −1.347 531 604 7

−4.465 −4.465 714 822 8

−4.462 −2.31 857 991 9

−4.581 −2.334 899 1140 *HOMO, LUMO, singlet energy S1, and tripletenergy T1 were calculated within the Gaussian16 software package usingthe B3LYP hybrid functional set and cep-31G basis set. S1 and T1 wereobtained using TDDFT at the optimized ground state geometry. A continuumsolvent model was applied to simulate tetrahydrofuran solvent.

The DFT data indicates that heteroleptic, bis tridenate Os(II)-carbenecompounds, e.g. compounds 2-9, provide an operating design range toextend the light emission of a phosphorescent OLED from about 550 nm toabout 1200 nm by simply changing out a tridentate L_(B) ligand. Asshown, the light emission can be tuned from green (compound 5 and 6),yellow (compound 3 and 4), red (compound 2) and even reach near IR range(compound 7, 8 and 9).

The calculations obtained with the above-identified DFT functional setand basis set are theoretical. Computational composite protocols, suchas the Gaussian09 with B3LYP and CEP-31G protocol used herein, rely onthe assumption that electronic effects are additive and, therefore,larger basis sets can be used to extrapolate to the complete basis set(CBS) limit. However, when the goal of a study is to understandvariations in HOMO, LUMO, S₁, T₁, bond dissociation energies, etc. overa series of structurally-related compounds, the additive effects areexpected to be similar. Accordingly, while absolute errors from usingthe B3LYP may be significant compared to other computational methods,the relative differences between the HOMO, LUMO, S₁, T₁, and bonddissociation energy values calculated with B3LYP protocol are expectedto reproduce experiment quite well. See, e.g., Hong et al., Chem. Mater.2016, 28, 5791-98, 5792-93 and Supplemental Information (discussing thereliability of DFT calculations in the context of OLED materials).Moreover, with respect to iridium or platinum complexes that are usefulin the OLED art, the data obtained from DFT calculations correlates verywell to actual experimental data. See Tavasli et al., J. Mater. Chem.2012, 22, 6419-29, 6422 (Table 3) (showing DFT calculations closelycorrelating with actual data for a variety of emissive complexes);Morello, G. R., J. Mol. Model. 2017, 23:174 (studying of a variety ofDFT functional sets and basis sets and concluding the combination ofB3LYP and CEP-31G is particularly accurate for emissive complexes).

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

We claim:
 1. A compound of the formula ML_(A)L_(B); wherein ligand L_(A)is of Formula I, and ligand L_(B) is of Formula II

wherein M is selected from Os(II) or Ru(II), and the compoundML_(A)L_(B) has a formal neutral charge; rings A, B, C, D, E, and F areindependently a 5-membered or 6-membered aromatic ring, and R^(A),R^(B), R^(C), R^(D), R^(E), and R^(F) each independently represent monoto the maximum allowable substitution, or no substitution; L¹, L², L³,and L⁴ independently represent a single bond or an organic linkinggroup; W¹, W², W³, and W⁴ are independently selected from carbon ornitrogen; Y¹, Y², Y³, and Y⁴ are independently selected from carbon ornitrogen; Z¹, Z², and Z³ are independently selected from carbon ornitrogen, and at least one of Z¹, Z², and Z³ is nitrogen; wherein eachR^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) are independently hydrogenor a substituent selected from the group consisting of deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, or optionally, any two adjacent substituents of R^(A), R^(B),R^(C), R^(D), R^(E), or R^(F), can join to form a ring.
 2. The compoundof claim 1, wherein R^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) areselected from the group consisting of deuterium, fluorine, alkyl,cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile,sulfanyl, and combinations thereof.
 3. The compound of claim 1, whereintwo of Z¹, Z², and Z³ is nitrogen.
 4. The compound of claim 1, whereinZ¹ is carbon, and ring D is selected from benzene, naphthyl, or anaza-analog of each thereof; each of which is optionally substituted; andZ² and Z³ are nitrogen, or one of Z² and Z³ is nitrogen, and the otheris a carbene carbon.
 5. The compound of claim 1, wherein two of rings A,B, and C is an N-heterocyclic carbene ring each with a carbene carboncoordinated to the metal M.
 6. The compound of claim 5, wherein ring Aand ring C are the N-heterocyclic carbene rings, and ring B is selectedfrom benzene, naphthyl, or an aza-analog of each thereof; each of whichis optionally substituted.
 7. The compound of claim 1, wherein L¹, L²,L³, and L⁴ are each a direct bond; each of W¹, W², W³, and W⁴ arecarbon, and ring B is an optionally substituted benzene.
 8. The compoundof claim 1, wherein L_(A) is selected from the group consisting of:

wherein X¹, X², and X³ are independently selected from C or N; R, R′,R¹, R², and R³ are independently hydrogen or a substituent selected fromthe group consisting of deuterium, halogen, alkyl, cycloalkyl,heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; or optionally, any twoadjacent substituents of R¹, R², and R³ can join to form a ring withring.
 9. The compound of claim 8, wherein each of X¹, X², and X³ is C,and form a benzene ring, which is optionally substituted with R². 10.The compound of claim 8, wherein two of R¹, two of R², and/or two of R³join to form a fused benzene ring or an aza-analog thereof; and eachfused ring is optionally substituted.
 11. The compound of claim 1,wherein the ligand L_(A) is selected from the group consisting of


12. The compound of claim 1, wherein the ligand L_(B) is selected fromthe group consisting of

wherein X⁶, X⁷, X⁸, X⁹, X¹⁰, X¹¹, X¹², X¹³, and X¹⁴ are eachindependently selected from C or N, and each 6-membered aromatic ringhas no more than three N; and R″, R⁴, R⁵, and R⁶ are independentlyhydrogen or a substituent selected from the group consisting ofdeuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof; or optionally, any two adjacent substituents ofR⁴, R⁵, and R⁶ can join to form a ring with ring.
 13. The compound ofclaim 12, wherein the ligand L_(B) is selected from the group consistingof

wherein X⁶, X⁷, X⁸, X⁹, X¹⁰, X¹¹, X¹², X¹³, and X¹⁴ are eachindependently selected from C or N, and each 6-membered aromatic ringhas no more than three N; and R″, R⁴, R⁵, and R⁶ are independentlyhydrogen or a substituent selected from the group consisting ofdeuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof; or optionally, any two adjacent substituents ofR⁴, R⁵, and R⁶ can join to form a ring with ring.
 14. The compound ofclaim 1, wherein the ligand L_(B) is selected from the group consistingof


15. The compound of claim 14, wherein the compound is the Compound xhaving the formula M(L_(Ai))(L_(Bj)); wherein x=151i+j−151; i is aninteger from 1 to 68; and j is an integer from 1 to 151; and whereinL_(Ai) has the following structure:


16. An organic light emitting device (OLED) comprising an anode, acathode, and an organic layer disposed between the anode and thecathode, the organic layer comprising a compound of the formulaML_(A)L_(B); wherein ligand L_(A) is of Formula I, and ligand L_(B) isof Formula II

wherein M is selected from Os(II) or Ru(II), and the compoundML_(A)L_(B) has a formal neutral charge; rings A, B, C, D, E, and F areindependently a 5-membered or 6-membered aromatic ring, and R^(A),R^(B), R^(C), R^(D), R^(E), and R^(F) each independently represent monoto the maximum allowable substitution, or no substitution; L¹, L², L³,and L⁴ independently represent a single bond or an organic linkinggroup; W¹, W², W³, and W⁴ are independently selected from carbon ornitrogen; Y¹, Y², Y³, and Y⁴ are independently selected from carbon ornitrogen; Z¹, Z², and Z³ are independently selected from carbon ornitrogen, and at least one of Z¹, Z², and Z³ is nitrogen; wherein eachR^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) are independently hydrogenor a substituent selected from the group consisting of deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, or optionally, any two adjacent substituents of R^(A), R^(B),R^(C), R^(D), R^(E), or R^(F), can join to form a ring.
 17. The OLED ofclaim 16, wherein the organic layer further comprises a host, whereinthe host comprises at least one chemical group selected from the groupconsisting of triphenylene, carbazole, dibenzothiophene, dibenzofuran,dibenzoselenophene, azatriphenylene, azacarbazole, aza-dibenzothiophene,aza-dibenzofuran, and aza-dibenzoselenophene.
 18. The OLED of claim 16,wherein the organic layer provides light emission in a range selectedfrom the group consisting of: from 700 nm to 1200 nm, from 800 nm to1200 nm, from 900 nm to 1200 nm, and from 1000 nm to 1200 nm.
 19. Aconsumer product comprising an organic light-emitting device (OLED)comprising: an anode, a cathode, and an organic layer disposed betweenthe anode and the cathode, the organic layer comprising a compound ofthe formula ML_(A)L_(B); wherein ligand L_(A) is of Formula I, andligand L_(B) is of Formula II

wherein M is selected from Os(II) or Ru(II), and the compoundML_(A)L_(B) has a formal neutral charge; rings A, B, C, D, E, and F areindependently a 5-membered or 6-membered aromatic ring, and R^(A),R^(B), R^(C), R^(D), R^(E), and R^(F) each independently represent monoto the maximum allowable substitution, or no substitution; L¹, L², L³,and L⁴ independently represent a single bond or an organic linkinggroup; W¹, W², W³, and W⁴ are independently selected from carbon ornitrogen; Y¹, Y², Y³, and Y⁴ are independently selected from carbon ornitrogen; Z¹, Z², and Z³ are independently selected from carbon ornitrogen, and at least one of Z¹, Z², and Z³ is nitrogen; wherein eachR^(A), R^(B), R^(C), R^(D), R^(E), and R^(F) are independently hydrogenor a substituent selected from the group consisting of deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, or optionally, any two adjacent substituents of R^(A), R^(B),R^(C), R^(D), R^(E), or R^(F), can join to form a ring; wherein theconsumer product is selected from the group consisting of a flat paneldisplay, a computer monitor, a medical monitor, a television, abillboard, a light for interior or exterior illumination and/orsignaling, a heads-up display, a fully or partially transparent display,a flexible display, a laser printer, a telephone, a cell phone, tablet,a phablet, a personal digital assistant (PDA), a wearable device, alaptop computer, a digital camera, a camcorder, a viewfinder, amicro-display that is less than 2 inches diagonal, a 3-D display, avirtual reality or augmented reality display, a vehicle, a video wallcomprising multiple displays tiled together, a theater or stadiumscreen, a light therapy device, and a sign.
 20. A formulation comprisinga compound in accordance with claim 1.